A screen printing method is used to produce electrodes in a solar cell and a display unit such as a liquid crystal display, a plasma display, and an organic electro luminescence (EL) display. In the screen printing method, a printing mask formed with a predetermined pattern thereon is used. The printing mask is placed at a predetermined distance from an object to be printed placed on a printing stage, and paste including an electrode material is supplied on the printing mask. The paste is spread on the printing mask by a squeegee, and only the paste on a meshed area is applied to the object to be printed. The paste applied to the object to be printed is baked at a predetermined temperature depending on the electrode material, and thereby the electrode is formed.
The printing stage used for the screen printing includes a stage surface and a vacuum conduit. The stage surface is formed with a plurality of suction holes and the object to be printed is placed on the stage surface. The vacuum conduit communicates with the suction holes, and is formed within a main body of the printing stage below the stage surface. The printing stage aligns and fixes the object to be printed by vacuum contact the object to be printed with the stage surface that includes the suction holes using a vacuum line connected to the vacuum conduit.
To form the electrode on a substrate of the solar cell by the screen printing method, the object to be printed is placed immediately on the stage surface that includes the suction holes. When the solar cell cracks during a printing process, debris of the solar cell or a printing paste clot is sucked from the suction hole of the printing stage into the suction hole and the vacuum conduit. After natural drying, the vacuum state is forcibly terminated by blowing air into the suction holes to remove the substrate before placing another substrate on the printing stage. At this time, the paste clot or the debris of the cell pops out of the suction hole and gets between the stage surface and the substrate to damage the substrate of the solar cell to be printed on.
Patent document 1 discloses a technology of providing a sponge as a cushion below a printed circuit board (PCB) to be printed on so that solder paste is evenly printed on the PCB and parts on the PCB are not damaged.
Patent document 1: Japanese Patent Laid-open No. H04-199895